calcvar

sofia_redux.instruments.forcast.calcvar.calcvar(data, header)

Calculate read and poisson noise of the variance from raw FORCAST images

Calculates the read noise and poisson noise components of the variance from raw FORCAST images. The following equation is used to derive the variance for each pixel:

V = N * betaG/g + RN^2/g^2

where V is the variance, N is the raw ADU in each pixel, betaG is the excess noise factor, g is the fain, and RN is the read noise in electrons. g comes from the EPERADU keyword in the FITS header. RN is determined by the instrument team, but its value depends on the capacitance setting (recorded in the ILOWCAP keyword in the FITS header). betaG is also determined by the instrument team.

Parameters:

datanumpy.ndarray

Raw image array

headerastropy.io.fits.header.Header

Raw image header; will be updated with HISTORY message and keywords

Returns:

numpy.ndarray

Image array with the same dimensions as the input raw image containing the calculated variance.